Turn on default ink drop handling for new tab button.

InkDropGestureHandler is now InkDropEventHandler and handles mouse and
gesture events.
https://chromium-review.googlesource.com/c/chromium/src/+/1344262

Bug: 910050
Change-Id: Iab91ca41f100cf3d0ba34b54112bc1fecf49406d
Reviewed-on: https://chromium-review.googlesource.com/c/1355490Reviewed-by: Peter Boström <pbos@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612387}

chrome/browser/ui/views/tabs/new_tab_button.cc

@@ -72,7 +72,7 @@ NewTabButton::NewTabButton(TabStrip* tab_strip, views::ButtonListener* listener)
   ink_drop_container_ = new views::InkDropContainerView();
   AddChildView(ink_drop_container_);
   ink_drop_container_->SetVisible(false);
-  SetInkDropMode(InkDropMode::ON_NO_GESTURE_HANDLER);
+  SetInkDropMode(InkDropMode::ON);
   set_ink_drop_visible_opacity(0.08f);
 
   SetFocusPainter(nullptr);